1. Field of the Invention
The present invention relates to a cathode ray tube including an electron gun for generating electron beams to display an image, and more particularly to a cathode ray tube which prevents a getter which is served for increasing a degree of vacuum in the inside of the cathode ray tube and for maintaining the degree of vacuum from being scattered to an electron gun side and deteriorating characteristics of the electron gun.
2. Description of the Related Art
For increasing the degree of vacuum in the inside of the cathode ray tube and for maintaining the degree of vacuum over a long period, it is necessary to scatter the getter in the inside of the cathode ray tube. The getter is formed of a metal film made of barium Ba and is scattered over a wide range in the inside of the cathode ray tube to perform a function of absorbing a generated gas. However, when the metal film which originally possesses a low work function is scattered and adheres to electrodes of the electron gun, stray electrons are generated from the metal film. That is, a withstand voltage between electrodes of the electron gun is lowered. Further, phosphors emit light due to the stray electrons thus exerting an adverse influence to an image.
In Japanese Patent Laid-open 2001-93449, there is disclosed a color cathode ray tube in which a getter is arranged between a funnel and an inner shield arranged close to an inner surface of the funnel, a control plate which controls the scattering of a getter vapor from the getter in the direction other than the electron-gun direction is provided to the getter thus forming a getter film over a wide range without allowing the getter vapor to adhere to a color selection electrode and the electron gun.